Catalytic esterification



mama Aug. 18, 1931 UNITED v STATES PATENT oFFicE ALPHONB O. JAEGEB, OFGRAFTON, PENNSYLVANIA, ASSIGNOB TO THE SELDER COMPANY, OF PITTSBURGH,PENNSYLVANIA, A CORPORATION 01 DELAWARE CATALYTIC ssrnaincarron HoDrawing. Original application filed March 23, 1928, Serial No. 284,275.Divided and this application filed March 28, 1929. Serial No. 350,830.

This invention relates to vapor phase of catalytic esterifications.

According to the present invention, esterifications are carried out inthe vaporphase in the presence of a new class of contact masses. Thecontact masses used in the present invention contain base exchangebodies or their derivatives. Under the term base exchange body areincluded all nat--,

ural or artificial bodies which possess the properties of exchangingtheir bases for other bases of salt solutions. The base exchangingproducts used in making catalytic compositions of the present inventionor as initial material for derivatives'to be so used may possess highbase exchanging power or in many cases may possess lower base exchangingpower, since the catalytic value of the final compositions is notprimarily dependent on the amount of base exchanging power present. Ingeneral the base exchange bodies may be divided into two maincategories:two-component and multicomponent zeolites, i. e., baseexchange bodies containing chemically combined silicon in their nucleusand non-silicious base exchange bodies in which all of the silicon isreplaced by other suitable acidic or amphotheric metal oxides.Two-component zeolites are the reaction products of two types of initialcomponents, that is to say, metallates and silicates,, (using 'the termsmetallate in a somewhat broader sense as will be defined further on inthe description), or .metal salts and silicates.

quently more than one member of a type may enter into reaction, that isto say, a sil-' icate may react with more than one metalv late or morethan one metal salt. The multicomponent zeolites are the reactionproducts of at least three types of components, that is to say, at leastone silicate, at least one metallate, and at least onemezal salt.

The base exchanging bodies, both zeolites 4 and non-silicious baseexchange bodies, may

be associated with diluents preferably in the form of a physicallyhomogeneous structure, as will be described below. Either diluted orundiluted base exchange bodies may be present in the contact masses usedin the Frepresent invention, or their derivatives may physicalc'haracteristicsof the parent base exchange bodies. Such derivatives maybe salt-like bodies, that is to say, the reaction products of baseexchange bodies with compounds containing anions capable of reactingwith the base exchange bodies to form products which possess many of theproperties of salts. A further class of derivatives are the acid leachedbase exchange bodies. When a base exchange body is subjected to leachingby acids, particularly dilute mineral acids, the exchangeable bases arefirst gradually removed. The resulting products contain both the morebasic and the more acidic components of the non-exchangeable nucleus ofthe base exchange body, with or without a portion of the exchangeablebases. As the leachin is carried on further, more and more 0 therelatively positive components of the non-exchangeable nucleus areremoved, and if carried to completion the leached product contains onlythe relatively acid, components of the non-exchangeable nucleus. In thecase ofzeolit'es the final product fromlong continued leaching is acomplex silicic acid which has many' of the physical properties oftheoriginal base exchange body. In the description and claims the class ofbase exchange bodies and their derivative will be referred to by thegenericterm permutogenetic products.

Catalytically active components may be associated with diluted orundiluted, permutogenetic bodies in four main forms, as follows :-(1)They maybe physically admixed with or impregnated into thepermutogenetic products. (2) They may be physically homogeneouslyincorporated into the of catalytically active dilutent bodies or in theform of diluents which have been impregnated with catalytically activesubstances. (3) They may be chemically Combined with or in thepermutogenetic products in non-exchai'igeable form, that is to say, theymay form a part of the non-exchangeable nucleus of the base exchangebody present in the final contact mass or which is transformed into thederivatives, or they may be chemically combined with the base exchangebodies in the form of catalytically active anions which form with thebase exchange body salt-like bodies. (4) They may be chemically combinedin exchangeable form either during the formation of the base exchangebody or by base exchange after formation. Obviously of course the sameor different catalytically active components may be present in more thanone of the above described forms, and it is an advantage of the presentinvention that catalytically active substances may be introduced in awide variety of forms which give a large field of choice to thecatalytic chemist.

While the different permutogenetic products may vary widely in theirchemical characteristics, they all possess a similar physical structurewhich is characterized by more or less high porosity, frequentlymicroporosity, and great resistance to high temperatures, and in thecase of products which have not been acid leached to the point ofremoval of catalytically active components these components aredistributed throughout the framework of the products in atomic ormolecular dispersion, as will be described in greater detail below, andthis chemical homogeneity is one of the important advantages of some ofthe contact masses of the present invention.

While three of the methods of combination of the catalytically activesubstances may be effected with undiluted as well as dilutedpermutogenetic products, it has been found that for most reactionshomogeneously diluted permutogenetic contact masses are of advantage,particularly where the diluents are of a hysical nature such as to exerta desired in of the contact masses, as when, for example, diluents arerich in silica, which has been found to have an activating power, orwhere the diluents by reason of high porosity, capillarity, or surfaceenergy may be considered as physical catalysts or activators.

Base exchange bodies used in contact masses of the present inventionbehave as if they were products of extremely high molecular weight forcatalytically active components can be introduced either in thenonexchangeable nucleus or in the form of exchangeable bases inpractically any desirable proportions and the ordinary law of chemicalcombining proportions, which in comical analysis.

vfinely and I tact masses for. the molecular association of uence on acatalytic activitypounds of low molecular weight restricts theproportions in which components can be incorporated chemically, appears.to be without Iorce, which makes it reasonable to assume that themolecular weight is so high as to completely mask the effect of the law.It is of course possible that the base exchange bodies, or some of them,may be solid solutions of a plurality of related compounds of lowermolecular weight. it has not been possible hitherto to definitely settlethis question, asbase exchange bodies are not readily capable ofstructural chem- The present invention is of course not limited to anytheory, but irrespective of the underlying reasons the fact thatcatalytically active components may be chemically introduced in anydesired proportions is of enormous importance to the catalytic chemistand gives him the power to produce an almost unlimited number ofgradually toned catalysts or conorganic compounds and in all cases thecontact masses produced are highly effective by reason of the desirablephysical structure of the permutogenetic products contained therein andthe wide limits of homogeneous dilution of catalytically activemolecules or atoms with resulting uniformity and smoothness of action,which is of great importance, particularly in the sensitive reactionsfor which contact masses used in the present invention are peculiarlyadapted.

In addition to the important characteristics with which permutogeneticproducts endow the contact masses of the present invention it has beenfound that for many of the reactions coming within the scope of thepresent invention, it is desirable to stabilize the contact masses, andthis may be effected by associating with the permutogenetic products orincorporating or form ing therein compounds of the alkali formingmetals, that is to say, the alkali metals, the alkaline earth metals,and the strongly basic earth metals. These compounds appear to slow upor smooth out the catalytic reaction, and will be referred to throughoutthis specitication as stabilizers. The stabilizers may be non-alkaline,weakly alkaline or strongly alkaline, depending on the reaction productsand on the nature of the catalytically active components used. It is agreat mlvantage of the present invention that in the normal formation ofbase exchange bodies alkali forming metal oxides are present asexchangeable bases, and whether used without acid treatment or treatedwith acid, they form stabilizers which are combined in or associatedwith the resulting permutogi-inetic products in an extremely fine stateof division in which the stabilizers are peculiarly active. Thus baseexchange bodies containing alkali forming metal exchangeable bases maybeconsidered as complex stabilizers. 4

In addition to the use of stabilizers which are important in a largenumber of molecular associations included in the scope of the presentinvention, it has been found that the stabilizer action and the overallefficiency of the contact masses can in many cases be greatly increasedor enhanced by theassociation therewith or chemlcal comb1na-- obtainingwill be referred to throughout the specification as stabilizerpromoters, as they appear to enhance the toning effect which can beachieved bystabilizers. The use of this expression should, however, inno sense be taken to limit the invention to a particular theory ofaction of these non-specific catalysts and in fact in some casesstabilizer promoter may be present where there are no stabilizers.

The tremendous range of chemical groups which ma be combined in or withor incorporate in permutogenetic products per mit a wide choice ofstabilizer promoters as well as specific catalysts and permits theirassociation with the contact masses in an extremely homogeneous andcatalytically eflicieut form. Thus many base exchange bodies or theirderivatives may be considered as complex catalysts, stabilizers andstabilizer promoters, as all of these elements may be present in thesame chemical compound and sharing the advantages flowing from itsdesirable ph s-ical structure and chemical properties. f course bothstabilizer and stabilizer promoter may be mixed partly or wholly withpermutogenetic products and a single stabilizer or single stabilizerpromoter may be present partly in physical admixture and partly inchemical combination, as will be clear to the skilled base exchangechemist.

The base exchange bodies which form the important components or initialmaterial for derivatives in contact masses of the pre sent invention maybe prepared by any of the well known methods. Thus, for example,two-component zeolites may be prepared by wet methods in whichthemetallate components or metal salt components, part or all of which maybe catalytically active, are caused to react with soluble silicates toform zeolites of alumino silicate or aluminum double silicate types, orthe components may be fused, referably in the presence of fluxes. Itshould e understood that under the term metallate is included not onlythe alkaline solutions of amphoteric metal oxides or hydroxides but alsoalkali forming metal salts of metals acids, such as the oxyacids ofmetals of the fifth and sixth groups, which in at least one stage ofoxidation are not strictly speaking amphoteric, but which products arecapable of reacting with silicates to form zeolites, or with othercomonents to form non-silicious base exchange odies." Throughout the secification this somewhat more general de nition of metallates will bestrictly adhered to. In the formation of two-component zeolites by. wetmethods, the final reaction product must be alkaline to litmus, and forproducts of high base exchanging power it should be neutral or alkalineto phenolphthalein. For the purpose of producing base exchan e bodies tobe used in the preparation 0 contact masses of the present invention itis sometimes unnecessary to provide high base exchanging power, and formany purposes zeolites formed under conditions resulting in a finalreaction which is acid to phenolphthalein but alkaline to litmus are ofadvantage. It is not definitely known whether products produced undersuch circumstances are homogeneous chemical compounds, although in manyways they behave as such. There is, however, reason to believe that insome cases at least mixtures of base exchanging and non-base exchangingpolysilicatcs may be produced. For the purpose of the presentspecification a product will be considered as a base exchange product ifit has any base exchange power at all.

It is desirable for many purposes, and particularly where two-componentzeolites of high base exchanging power are needed, to add to therelativel acid component, for example,metal salts 1n the case ofaluminum double silicate type of silicates, to the relatively morealkaline components such as, for example, soluble silicates. By thesemeans a continuous alkalinity is insured, and this method may beconsidered as the preferred method in most cases, but the oppositeprocedure is advantageous for certain contact masses and is included inthe invention.

Multi-component zeolites may be prepared by any of the foregoing methodsusing at least three types of components, that is to sa at least onemetallate, at least one metal sa t and at least one soluble silicate. Inthe case of multicomponent zeolites, as in the case of two-componentzeolites, the conditions of alkalinity should be observed, and for manypurposes it is advantageous to add the relatively acid components to therelatively alkaline components in order to insure continuous alkalinereaction. The multi-component zeolites produced vary in their nature,dependent on the proportion of the different reacting components. Thuswhere the metallates and silicates predominate over the metal salts theresulting products resemble the alumino silicate type of two-componentzeolites. If the metal salts and silicates predominate over the.metallates the products resemble the aluminum double silicate type oftwo-component zeolites, and finally if the metallates and metal saltspredominate over the silicates the resulting product resembles more orless nonsilicious base exchange bodies. It will be clear that there isno sharpdefining line between the three types of multi-componentzeolites, and one shades into the other as the proportions of thedifferent components vary. It is an advantageof the multi-componentzeolites over the two-component zeolites that the choice ofcatalytically active components is wider, as some catalytically activeelements or groups can only be incorporated in the form of metallatesand others only in the form of metal salts. In a multi-component zeoliteeach catalytically active group can be incorporated in the form in whichit is best available.

Non-silicious base exchange bodies are produced by the general methodsdescribed above, but instead of bringing about reactions betweensilicates and other metal oxide components, two or more oxymetalconipounds are caused to react, in general, at least one will be ametallate and at least one a metal salt, or in some cases it is possibleto bring about action between two different metallates in which onenegative rad ical is more acidic than the other. It is possible toproduce non-silicious base exchange bodies in which a single metal ispresent. Thus for example, some metals may be sufficiently amphoteric incharacter to form both metallates and metal salts which are capable ofreacting with each other to produce base exchange bodies.

special method of producing nonsilieious base exchange bodies consistsin the gradual neutralization of strongly alkaline salts of the oxyacidsof metal elements of the fifth and sixth groups in stages of oxidationin which they are sufficiently amphoteric. The neutralization of otherstrongly alkaline metallates may also bring about formation ofnon-silicious base exchange bodies. The converse method,wherehynonalkaline salts of suitable metals are gradually treated withalkali until the reaction is sufficiently alkaline to permit theformation of base exchange bodies, .may also be used.

Many metals arerapable of entering into the base exchange formation onlyin certain stages of oxidation, and it is sometimes necessary tointroduce such metals in a stage of oxidation different from thatdesired in the final base exchange body, the change of stage ofoxidation being preferablyv ef-' fected during the formation of the baseexchange body. Certain other elements may be incorporated in the form ofcomplex compounds of the most various types, such as for example,ammonia complexes and the like.

In addition to the artificial base exchange bodies briefly describedabove, neutral base exchange bodies, such as nepheline, leucite,felspar, and the like, may be used.

The most important contact masses for many reactions containpermutogenetic products, in which preferably the diluents arehomogeneously incorporated into the base exchange bodies beforeformation of the latter, or at least before the base exchange body hasset after formation. Many diluents, both inert, stabilizing, activating,catalytically active, or having stabilizer pro-- moter effects, can beused. A few of the diluents will be briefly enumerated :kieselguhrs ofall kinds, particularly natural or treated celite earth, silicouspowders of various types, powdered permutogenetic products, natural orartificial powders of rocks, stones, tuffs, trass, lava, and similarlyvolcanic products which are frequently highly porous, greensand,glauconite or its acid leached derivative glaucosil, pulverized slagwool, cements, sand, silica gel, pulverized earthenware, fullers earth,talc, glass powder, pumice 1neal,.asbestos, graphite, activated carbon,quartz meal, various pulverized minerals rich in quartz, metal powdersand metal alloy powders, salts of oxymetal acids such as tungstates,vanadates, chromates, uranates, manganates, cerates, molybdates, etc.,particularly copper salts of the above silicates, such as coppersilicate, iron silicate, nickel silicate, cobalt silicate, aluminumsilicate, titanium silicate, minerals or ores, especially those rich incopper, etc. Finely divided diluents are of great advantage, especiallywhen the average particle size is less than 60 microns, in which casethediluents possess high surface energy, which increases the adsorptive andabsorptive capacity of the contact mass, the diffusion speed andporosity. These finely divided diluents may be considered as physicalcatalysts or activators. Diluted ermutogenetic bodies may also be finelydivided and used as part or all of the diluents of other base exchangebodies.

The following nine methods are the most effective for the introductionof diluents, but any other suitable methods can be used:

(1) The diluents may be mixed with one or more liquid components of thebase exchange bodies to be formed when the latter are prepared by wetmethods.

(2) Components, either catalytically active, stabilizer promoters, orothers, may be precipitated or impregnated into diluent bodies which arethen incorporated into the base exchange bodies by any suitable methodsof incorporation.

(3) Diluents may be mixed with base exchange bodies when the latter arestill in the form of gels, 'by kneading or stirring, in which case thebase exchange gel behaves as an adhesive. The homogeneity and uniformityof the distribution of the diluents is of course not quite so great bythis method as by method (1), but for the catalytic molecularassociation of organic compounds extreme uniformity is not essential.

(4) Diluents may be formed during the formation of base exchange bodiesby mixing suitable compounds with the components of the base exchangebodies so that the diluent particles are precipitated during formation.Protective colloids may be added to prevent coagulation of the diluentparticles before the base exchange bodies have become sufiiciently set.

(5) Compounds may be added which react with certain of the base exchangebodies forming components to produce diluents, for instance salts of themetal acids of the fifth and sixth groups may be added insuflicientexcess so that they react with components of the base exchangebody to form insoluble diluents, as for example the heavy metal oxides'(6) Preformed base exchange bodies, diluted or undiluted, artificial ornatural, can be impregnated with true or colloidal solutions ofcatalytically efi'ective components and then dried.

(7 A preformed base exchange body, diluted or undiluted, may beimpregnated with a plurality of solutions which react therein toprecipitate any desired diluents.

(8) Soluble diluent compounds may be added to the components forming abase exchange body, which after formation retains the compounds insolution and is dried without washing or is treated to precipitate thecompounds.

(9) Natural base exchange bodies or artificial base exchange bodies,diluted or undiluted, or their derivatives, may be impregnated withsolutions of the desired compounds, which are then precipitated by meansof reactive gases.

'The nucleus or non-exchangeable portion of the molecules of the baseexchange bodies is ordinarily considered to consistof two types ofoxides, namely, relatively basic metal oxides, usually amphoteric, andrelatively acidic oxides, such as SiO some amphoteric metal oxides andsome metal oxides which have a distinctly acid character. The nucleusbehaves as a single anion and cannot be split by ordinary chemicalmeans, but it is advantageous to consider the two ortions of the nucleusas the basic and aci ic portions, bearing in mind of course that thenucleus behaves as a single grou capa le of forming the basic portion ofthe nucleus are those of the following metals :copper, silver, gold,bismuth, beryllium, zinc, cadmium, boron, aluminum, some rare earths,titanium, zirconium, tin, lead, thorium, niobium, antimony, tantalum,chromium, molybdenum, tungsten, uranium, vanadium, manganese, iron,nickel, cobalt, platinum, palladium. Compounds of these elements maybeintroduced singly or in mixtures, in any desired proportions, and may bein the form of simple or complex ions. It should be understood that someof the elements in certain stages of oxidation may be introduced eitheras metallates or metal salts. Others may be introduced in only one form,and still others may be introduced in a stage of oxidation other thanthat desired in the final base exchange body or in the form of complexcompounds. Among the complex ionogens are ammonia, hydrocyanic acid,oxalic acid, formic acid, tartaric acid, citric acid, glycerine, and thelike.

Many of the metals are specific catalysts, others are stabilizers, andstill others are stabilizer promoters. Naturally the status of anelement as catalyst or stabilizer promoter will vary with the particularreaction for which the final contact mass is to be used, and the choiceof catalysts and stabilizer promoters together with the proportions willbe determined by the particular molecular association of organiccompounds forwhich the contact mass is to be used.

Examples of components forming the relatively acid portion of the baseexchange nucleus are alkali metal silicates, which are soluble inalkali, and alkali metal salts of acids, such as those of boron,phosphorous,

nitrogen, tin, titanium, vanadium, tungsten, chromium, niobium,tantalum, uranium, antimony, manganese, etc.

The exchangeable bases of the base exchange bodies may be substituted bybase exchange, and the elements which can be introduced singly or inadmixture by base ex change are the following :copper, silver, gold,ammonium, beryllium, calcium, manganese, caesium, potassium, sodium,zinc, strontium, cadmium, barium, lead, aluminum, scandium, titanium,zirconium, tin, antimony, thorium, vanadium, lithium, rubidium,thallium, bismuth, chromium, uranium, manganese, iron, cobalt, nickel,ruthenium, palladium, platinum and cerium.

Depending on the reactions in which the contact mass is to be used, theexchangeable vbases introduced may be specific catalysts,

they may be stabilizers, or they may be stabil zer promoters. They maybe introduced as simple ions or as complex ions, and may en- The metalcompounds which are containing the following elements :-chromium,vanadium, tungsten, uranium, molybdenum, manganese, tantalum, niobium,antimony, selenium, bismuth, tin, chlorine, platinum, boron. Among thecomplex radicals are ferro and ferricyanogen, certain ammonia complexesand the like. The amount of acid radicals caused to unite with the baseexchange bodies to form salt-like bodies may be varied so that theresulting products may possess the character of acid, neutral or basicsalts. Many of these acid radicals are stabilizers or stabilizerpromoters for the catalytic molecular associations of organic compounds.

The base exchange bodies diluted or undiluted, or some of their saltlike body derivatives, may be treated with acids, such as mineral acids,for example, 210% sulfuric, hydrochloric or nitric acids, to remove partor all of the exchangeable bases, or also part or all of the basicportion of the nucleus.

In the case of zeolites, the partial leaching with acids, which leavespart or all of the basic portion of the nucleus or even part of theexchangeable bases, does not affect the function of the zeolites ascatalysts when they contain catalytically active elements in the basicportion of the nucleus, or in some cases even exchangeable bases, andsuch partially leached catalysts are of great importance in manyreactions. Where the leaching is carried out to completion theadvantageous physical structure remains to a considerable extent thesame but the remainder is of course a form of silica, or in the case ofzeolites in which part of the silica is replaced by other acidiccompounds, a mixture of the two, and usually will not be a specificcatalyst for the reactions of the present invention. It serves, however,as an advantageous physical carrier of specific catalysts, and in thecase of partially substituted zeolites may also contain stabilizerpromoters.

Leached non-siliciousbase exchange bodies, either partially orcompletely leached, may contain catalytically active components andbehave as catalysts, stabilizer promoters or both, and many importantcatalysts are thus obtained. This is particularly the case for reactionswhere a relatively alkali-free contact mass is required for best resultsand where the alkali content of a contact mass containing a baseexchange body may be too great for optimum results.

telleurium, phosphorus,

Base exchange bodies or their derivatives,

diluted or undiluted, may also be coated in the form of films on massivecarrier granules or may be impregnated therein. The massive carriers maybe inert, activating, or themselves catalysts. For exam less, certaincatalytic metal alloys, and mmerals, fall within this class. Aluminum orcopper alloy granules perform an additional advantageous function inthat their relatively high heat conductivity tends to prevent localoverheating in exothermic reactions, which is of considerable importancein obtaining good yields, as the esterification reactions of the presentinvention are equilibrium reactions, and at higher temperatures theequilibrium may be adversely affected with resulting lowering of yieldsand contamination of. the product.

Ewample 50 parts of finely ground pumice meal are suspended in 250 partsof water, and a mixture of strong thorium nitrate and titanium nitratesolutions, containing 25 parts of thorium nitrate and 10 parts oftitanium nitrate, are added. Ammonia water is then added,'with vigorousagitation, or, if desired, a dilute alkalisolution may be added untilthe oxides of titanium and thorium are salt solution by means ofammonia, are

treated with a 2N. sodium hydroxide solution until the aluminumhydroxide dissolves as sodium aluminate. The waterglass-kieselguhrsuspension is then poured into the sodium aluminate solution and heatedto 5060 C. with vigorous agitation. An aluminum zeolite is obtained,diluted with kieselguhr containing thorium oxide and titanium oxide.The'yield may be increased by neutralizing the unnecessary excess ofalkali with dilute nitric acid. The product is then sucked off from themother liquor, washed in portions with 500 parts of water, and dried attemperatures preferably below 100 C. After drying the zeolite ishydrated with water in the usual way and again dried, followed byleaching with 12% nitric acid solution which is permitted to trickleover the zeolite in order to remove a maximum of exchangeable alkali.

The contact mass composition thus obtained is placed in a converter, anda mixture of organic acids and alcohols, preferably containing an excessof alcohol, is passed over the contact mass at 280350C., resulting ingoodyields of the corresponding esters. Examples of esterifications arethe production of the esters of benzoic,-ace tic, propionic or succinicacid, with ethyl, butyl, isobutyl or benzyl alcohols. It is sometimesadvantageous to pass a certain proportion of vapors of benzol and toluolover with alcohol and acid vapors, and

after condensing the product the benzol orum, titanium, zirconium, or amixture. This can be effected by trickling the corresponding saltsolutions over the baseexchange bodies. l

Other modified esterification contact masses are obtained by forming thesocalled salt-like bodies with themetal acids of the fifth or sixthgroup of the periodic system, such as for example the salt like bodies,which can be obtained by treating the base exchange bodies with 1%ammonium vanadate or tungstate solutions.

A useful esterification contact mass can also be obtained by causingsodium aluminate to react with thorium nitrate in proportions -so thatthe mixture remains alkaline to phenolphthalein. The non-siliciousbaseexchange body obtained, particularly when leached with dilute nitricacid to remove a maximum of exchangeable alkali, constitutes a veryeffective esterification contact mass.

This application is a division of my prior application Serial No.264,275, filed March In the claims the term permutogenetic covers baseexchange bodies, silicious or nonsilicious, the. products obtained bythe acid leaching of these base exchange bodies and the salt-like bodiesobtained by the reaction of these base exchange bodies with compoundsthe acid radicals of which are capable of reacting with the baseexchange bodies to produce products which show most of the properties ofsalts. When so used in the claims, the term permutogenetic will have noother meaning.

What is claimed as new is:

1. A method of esterification, which comprises vaporizing an organiccarboxylic acid and an alcohol and passing the vapors at an-elevatedtemperature over a contact mass containing at least one permutogeneticbody. I

2. A method of esterification, which comprises causing the vapors of anorganic carboxylic acid and an alcohol, admixed with the vapors of asubstance whichis relatively insoluble in water but forms therewith anazeotropic mixture, to pass at an elevated temperature over a contactmass containing at least one permutogenetic body.

3. A method according to claim 2 in lZvhich the added substance is ahydrocar- 4. A method according to claim 2 in which the added substanceis a hydrocarbon of the benzene series.

5. A method of vapor phase esterification, which comprises passing thevapors of an organic carboxylic acid and alcohol and a substancerelatively insoluble in water and capable of forming therewith anazeotropicmixture, to pass over a contact mass containing apermutogenetic body, condensing the reaction product and distilling offwater, and the product forming an azeotropic mixture therewith, togetherwith any excess al- 1 cohol present.

6. A method according to claim 1 in which the reaction is carried out ata temperature between 280350 C.

7. A method according to claim 1 in which the acid is benzoic acid.

8. A method of esterification which com prises causing the vapors of anorganic carboxylic acid and an alcohol, in admixture with the vapors ofa substance which is relatively insoluble in water but forms therewithan azeotro-pic mixture, to pass over an esterification catalyst atreaction temperatures.

9. A method of esterification which comprises causing the vapors of anorganic carboxylic acid and an alcohol, in admixture with the vapors ofa substance which is

